Like so many other objects these days, the bulky cathode-ray tube that produces images on most television sets and computer monitors is under pressure to slim down.
A trimmer picture tube would take up far less space in living rooms and on desktops.
Now two IBM scientists have come up with a cathode-ray tube, or CRT, that is only one inch thick. "Basically we banged holes in a magnet and fired electrons through the device" to create it, saidAndrew Knox, co-inventor of the technology. "That's the essence of the invention."
Knox, a senior research scientist specializing in electromagnetics and computer simulations at an IBM laboratory in Greenock, Scotland, developed the new picture tube with John Stuart Beeteson, now retired, whose field is displays.
The front of the new device, like that of a traditional cathode-ray tube, is coated with phosphor dots that light up when electron beams hit them. But the long paths that the electrons travel in old-fashioned picture tubes are eliminated, as are the electron gun assembly at the back of the tube and the bulbous shape of the tube itself.
Instead the new vacuum tube has a slender pair of rectangular glass plates that enclose its workings. One glass plate is coated with phosphors; the other covers the cathode that is the source of electrons. Between the two plates is the key to the new invention: a trim ceramic and stainless steel magnet full of tiny holes. An intense magnetic field within the holes applies a force to the electrons emitted from the flat cathode plate, causing them to spiral and focus into narrow beams.
Each beam of electrons accelerates out of its hole and hits a single pixel on the phosphor-covered glass. This battery of beams, each one aimed at a pixel, is quite different from the single beam of electrons that travels a long distance to the front of the conventional tube and deflects at a wide angle to cover a large screen.
"In essence, we have an electron gun for every single pixel," Knox said.
The magnetic plate and the other components are the equivalent of an electron gun assembly. The angle of deflection is reduced from the 90 to 110 degrees characteristic of a normal CRT to 1 degree, he said, a change that may translate into considerable space saved on the desktop.
The challenge of shrinking the bulky cathode-ray tube has vexed scientists for decades. Knox said the essence of his solution was the magnetic matrix that focuses each beam of electrons. "We used a magnetic field from a permanent magnet to collimate the electron beams," he said -- in other words, to have the electrons follow parallel paths instead of fanning out in a spray.
Frederic Kahn of Palo Alto, California, editor of a monthly industrial newsletter on display technologies, said he viewed the device as "a truly new invention."
"It has a much simpler structure than other currently pursued approaches to making flat panels," he said. The system does not require the thin film transistor arrays used in liquid crystal displays or the complex electrostatic grid structures required in a competing flat CRT technology called field emission display. Thus the new technology is "relatively simple and potentially cost-effective," Kahn said.
Because of its magnetic design, the device has the potential to be manufactured in mass quantities at a low price and to be used for resolutions ranging from those of conventional television sets to the higher ones of computer displays, Kahn said.
RSS